Concurrent schedules: How responses per reinforcer affects estimates of sensitivity to reinforcement

Conventionally, when choice is measured under concurrent schedules, all responses are included. However, the class of all responses consists of 2 sub-classes which are discriminable by their properties: Reinforced responses always equal obtained reinforcers, while unreinforced responses are free to vary. As a result, the inclusion of reinforced responses in choice measures results in sensitivity values in generalized matching that are biased toward larger values, and this bias becomes extreme in some combinations of overall response and reinforcer rates. Different ways of varying concurrent-schedule values also affect estimated sensitivity and the linearity between choice based on all responses and reinforcer ratios. To avoid spurious results and comparisons, and as a matter of good practice, generalized-matching fits and measures should be done using only unreinforced responses.